1. Field of the Invention
The present invention relates to an electronic component inspection equipment, and more particularly to an electronic component inspection equipment effective to prevent reflection of a virtual image.
2. Description of the Related Art
An electronic component such as a semiconductor device may be shipped in a state wrapped in an embossed tape or the like. Generally, the visual inspection of the electronic component is often conducted immediately before the wrapping. In practice, leads are inspected for their height and pitch deviation when the electronic component is accommodated in the embossed tape. An optical technique using a CCD camera or the like is preferable for the visual inspection of such electronic component.
When an electronic component housed in the embossed tape is optically pictured, however, virtual images of leads reflected in the side walls of the embossed tape might also be pictured other than the electronic component body. The virtual images of leads reflected in the side walls of the embossed tape make it difficult to judge an actual portion, possibly hindering the inspection.
Japanese Patent Application Laid-Open Publication No. 10-148517 has proposed an image pick-up technique in that the Brewster angle is used as means effective for preventing Ha phenomenon that the virtual image is reflected. This technique is based on the point that the reflection of a P polarized light wave becomes minimum at the Brewster angle and determines an image pick-up direction of a camera to be fat the Brewster angle to the walls of the embossed tape so to pick up an image of leads of the electronic component by irradiating a P polarized light wave from the determined position.
But, it was found that the above technique has a disadvantage that when it is used to inspect the leads of an electronic component, the leads are somewhat reflected, and its resolution is required. This problem is particularly conspicuous with QFP (Quad Flat Package).
Under the circumstances described above, it is an object of the present invention to provide an electronic component inspection equipment effective to prevent reflection of a virtual image.
To achieve the above object, a first aspect of the invention is an electronic component inspection equipment for optically inspecting an external shape of an electronic component (12) accommodated in a vessel (10), comprising: illumination means (M10) for irradiating illumination light (14) to the electronic component; image pick-up means (M12) which determines a direction satisfying a Brewster angle to a side wall (16) of the vessel as an image pick-up direction (18); and polarized light wave selection means (M14) which is disposed on the image pick-up direction to preferentially select a P polarized light wave to the side wall and leads the selected P polarized light wave to the image pick-up means.
A second aspect of the invention is in accordance with the first aspect of the invention in which the polarized light wave selection means (M14) is formed of a polarizer, and the image pick-up means is disposed on an optical path of the P polarized light wave selected by the polarizer.
A third aspect of the invention is in accordance with the second aspect of the invention in which the polarizer is a polarized light beam splitter.
A fourth aspect of the invention is in accordance with the second aspect of the invention in which the polarizer is a polarizing filter.
A fifth aspect of the invention is an electronic component inspection equipment for optically inspecting an external shape of an electronic component accommodated in a vessel (10), comprising: illumination means (M10) for irradiating illumination light (14) to the electronic component; image pick-up means (M12) which determines as image pick-up directions both a first direction (18-1) satisfying a Brewster angle to a first side wall (16-1) of the vessel and a second direction (18{circumflex over ( )}2) satisfying the Brewster angle toga second side wall (16-2) having an angle with respect to the first side wall; first selection means (M14-1) which is disposed on the first direction to preferentially select P polarized light wave to the first side wall and leads the selected P polarized light wave to the image pick-up means; and second selection means (M14-2) which is disposed on the second direction to preferentially select P polarized light wave to the second side wall and leads the selected P polarized light wave to the image pick-up means.
A sixth aspect of the invention is in accordance with the fifth aspect of the invention in which the first selection means and the second selection means are respectively formed of a polarizer, the image pick-up means is disposed on optical paths of the P polarized light wave to the first side wall and the P polarized light wave to the second side wall respectively selected by the individual polarizers.
A seventh aspect of the invention is in accordance with the fifth aspect of the invention in which the first selection means and the second selection means are formed of a single polarizer, {fraction (1/2)}xcex plate (32) which turns the oscillation direction of the P polarized light wave to the second side wall by 90 degrees is disposed between the polarizer and the second side wall, and the image pick-up means is disposed on an optical path of the P polarized light wave with respect to the first side wall selected by the polarizer.
An eighth aspect of the invention is in accordance with the sixth or seventh aspect of the invention in which the polarizer is a polarized light beam splitter.
A ninth aspect of the invention is in accordance with the sixth or seventh aspect of the invention in which the polarizer is a polarizing filter.